TWEAK Affects Keratinocyte G2/M Growth Arrest and Induces Apoptosis through the Translocation of the AIF Protein to the Nucleus

The soluble TNF-like weak inducer of apoptosis (TWEAK, TNFSF12) binds to the fibroblast growth factor-inducible 14 receptor (FN14, TNFRSF12A) on the cell membrane and induces multiple biological responses, such as proliferation, migration, differentiation, angiogenesis and apoptosis. Previous reports show that TWEAK, which does not contain a death domain in its cytoplasmic tail, induces the apoptosis of tumor cell lines through the induction of TNFα secretion. TWEAK induces apoptosis in human keratinocytes. Our experiments clearly demonstrate that TWEAK does not induce the secretion of TNFα or TRAIL proteins. The use of specific inhibitors and the absence of procaspase-3 cleavage suggest that the apoptosis of keratinocytes follows a caspase- and cathepsin B-independent pathway. Further investigation showed that TWEAK induces a decrease in the mitochondrial membrane potential of keratinocytes. Confocal microscopy showed that TWEAK induces the cleavage and the translocation of apoptosis inducing factor (AIF) from the mitochondria to the nucleus, thus initiating caspase-independent apoptosis. Moreover, TWEAK induces FOXO3 and GADD45 expression, cdc2 phosphorylation and cdc2 and cyclinB1 degradation, resulting in the arrest of cell growth at the G2/M phase. Finally, we report that TWEAK and FN14 are normally expressed in the basal layer of the physiological epidermis and are greatly enhanced in benign (psoriasis) and malignant (squamous cell carcinoma) skin pathologies that are characterized by an inflammatory component. TWEAK might play an essential role in skin homeostasis and pathology

Inhibition of Apoptosis Blocks Human Motor Neuron Cell Death in a Stem Cell Model of Spinal Muscular Atrophy

Spinal muscular atrophy (SMA) is a genetic disorder caused by a deletion of the survival motor neuron 1 gene leading to motor neuron loss, muscle atrophy, paralysis, and death. We show here that induced pluripotent stem cell (iPSC) lines generated from two Type I SMA subjects–one produced with lentiviral constructs and the second using a virus-free plasmid–based approach–recapitulate the disease phenotype and generate significantly fewer motor neurons at later developmental time periods in culture compared to two separate control subject iPSC lines. During motor neuron development, both SMA lines showed an increase in Fas ligand-mediated apoptosis and increased caspase-8 and-3 activation. Importantly, this could be mitigated by addition of either a Fas blocking antibody or a caspase-3 inhibitor. Together, these data further validate this human stem cell model of SMA, suggesting that specific inhibitors of apoptotic pathways may be beneficial for patients

Behavioral and Cognitive Improvement Induced by Novel Imidazoline I2 Receptor Ligands in Female SAMP8 Mice

As populations increase their life expectancy, age-related neurodegenerative disorders such as Alzheimer's disease have become more common. I2-Imidazoline receptors (I2-IR) are widely distributed in the central nervous system, and dysregulation of I2-IR in patients with neurodegenerative diseases has been reported, suggesting their implication in cognitive impairment. This evidence indicates that high-affinity selective I2-IR ligands potentially contribute to the delay of neurodegeneration. In vivo studies in the female senescence accelerated mouse-prone 8 mice have shown that treatment with I2-IR ligands, MCR5 and MCR9, produce beneficial effects in behavior and cognition. Changes in molecular pathways implicated in oxidative stress, inflammation, synaptic plasticity, and apoptotic cell death were also studied. Furthermore, treatments with these I2-IR ligands diminished the amyloid precursor protein processing pathway and increased Aβ degrading enzymes in the hippocampus of SAMP8 mice. These results collectively demonstrate the neuroprotective role of these new I2-IR ligands in a mouse model of brain aging through specific pathways and suggest their potential as therapeutic agents in brain disorders and age-related neurodegenerative diseases. Keywords Imidazoline I2 receptors (2-imidazolin-4-yl)phosphonates Behavior Cognition Neurodegeneration Neuroprotection Agin

Lymphocyte respiration in children with Trisomy 21

<p>Abstract</p> <p>Background</p> <p>This study measured lymphocyte mitochondrial O₂ consumption (cellular respiration) in children with trisomy 21.</p> <p>Methods</p> <p>Peripheral blood mononuclear cells were isolated from whole blood of trisomy 21 and control children and these cells were immediately used to measure cellular respiration rate. [O₂] was determined as a function of time from the phosphorescence decay rates (1/τ) of Pd (II)-<it>meso</it>-tetra-(4-sulfonatophenyl)-tetrabenzoporphyrin. In sealed vials containing lymphocytes and glucose as a respiratory substrate, [O₂] declined linearly with time, confirming the zero-order kinetics of O₂ conversion to H₂O by cytochrome oxidase. The rate of respiration (<it>k</it>, in μM O₂ min^-1), thus, was the negative of the slope of [O₂] <it>vs.</it> time. Cyanide inhibited O₂ consumption, confirming that oxidation occurred in the mitochondrial respiratory chain.</p> <p>Results</p> <p>For control children (age = 8.8 ± 5.6 years, n = 26), the mean (± SD) value of <it>k</it>_<it>c</it> (in μM O₂ per min per 10⁷ cells) was 1.36 ± 0.79 (coefficient of variation, Cv = 58%; median = 1.17; range = 0.60 to 3.12; -2SD = 0.61). For children with trisomy 21 (age = 7.2 ± 4.6 years, n = 26), the values of <it>k</it>_<it>c</it> were 0.82 ± 0.62 (Cv = 76%; median = 0.60; range = 0.20 to 2.80), <it>p</it><0.001. Similar results (<it>p</it><0.000) were obtained after excluding the five trisomy 21 children with elevated serum TSH (values >6.1 mU/L). Fourteen of 26 (54%) children with trisomy 21 had <it>k</it>_<it>c</it> values of 0.20 to 0.60 (i.e., <−2SD). The values of <it>k</it>_<it>c</it> positively correlated with body-mass index (BMI, <it>R</it> >0.302), serum creatinine (<it>R</it> >0.507), blood urea nitrogen (BUN, <it>R</it> >0.535) and albumin (<it>R</it> >0.446).</p> <p>Conclusions</p> <p>Children with trisomy 21 in this study have reduced lymphocyte bioenergetics. The clinical importance of this finding requires further studies.</p